The disclosures herein relate generally to computers and more particularly to an apparatus for cooling a heat generating component in a computer.
Many computers include electronic components such as a microprocessor that generate a considerable amount of heat. The performance and operating life of these components are adversely affected by excessive temperatures. As a result, it is necessary to use a cooling apparatus to control the operating temperature of these types of heat generating components.
In a portable computer, due to space constraints, the use of a cooling apparatus to control the operating temperature of the microprocessor is essential. Furthermore, it is critical that the cooling apparatus employed in a portable computer has suitable reserve capacity to ensure that the operating temperature can be controlled in a wide range of operating conditions. If the microprocessor temperature is not kept within a required temperature range, the performance and possibly the effective life of the microprocessor will be adversely affected.
The cooling efficiency in a typical cooling system that utilizes a heat pipe and a heat dissipating device is a function of the effective contact area at the heat source and at the heat dissipation device. The cooling efficiency is also a function of the heat carrying capacity of the heat pipe. To increase the cooling capacity, two heat pipes may be connected in a parallel configuration between the heat source and the heat dissipating device. The dual heat pipe configuration has the advantage of increasing the contact area at the heat dissipating device and at the heat source. Dual heat pipe configurations also benefit from the heat carrying capacity of two heat pipes.
The use of multiple heat pipes has a number of disadvantages over a single heat pipe. The disadvantages include added weight, higher cost, and less than optimal placement of the two heat pipes at the microprocessor due to geometry constraints. In addition, when a thermal transfer plate is used to make contact at the microprocessor, the placement of the heat pipes forces some of the heat to travel in an indirect path through the thermal junction plate between the microprocessor and the heat pipes. The effect of the heat traveling indirectly to the heat pipes is that the thermal resistance is increased.
Tolerance build up with two or more heat pipes is also a problem. The heat pipes act together to locate the thermal transfer plate on top of the microprocessor. Inaccuracies in forming the heat pipes can lead to a skewed relationship between the microprocessor and the thermal transfer plate. The skewed relationship results in increased thermal resistance and possibly excessive stress on the microprocessor, causing it to fracture.
U.S. Pat. No. 5,881,298 discloses a portable computer that conserves power when the computer operates from its portable power source. The portable computer has a processor operatively coupled to an input device, an output device, and a memory device. The portable computer also includes a portable power source operatively coupled to the processor, and a selectively operable cooling system that is adapted to create a heat transfer zone in which heat dissipates from the processor. The cooling system has a cooling unit that may be selectively disabled in a desired power-saving mode during which the processor may continue to operate. The cooling unit is preferably disabled by electrically disconnecting the cooling unit from the portable power source to de-energize the cooling system, or by physically disconnecting the cooling system from the portable computer.
U.S. Pat. No. 5,764,483 discloses a heat dissipating apparatus for efficiently transporting heat generated by components to a wall of a metal box that serves as a heat dissipation section. The heat generating components and the heat dissipation section are connected to each other through a thermal transport device having a flexible structure. The components and the box are connected to each other irrespective of the arrangement of components such that heat is efficiently transported by a liquid. In the heat dissipation section, because the components and the wall of the metal box are thermally connected to each other, a high heat dissipation capacity is obtained as heat is diffused extensively into the wall due to a high thermal conductivity of the metal box.
U.S. Pat. No. 5,339,214 discloses a computer chassis assembly that includes a heat pipe which thermally couples an electronic package to multiple fan units. The heat pipe provides a computer chassis that sufficiently cools internal heat generating components without placing the components in close proximity to the fans.
U.S. Pat. No. 4,931,905 discloses a cooling apparatus having two metal plates including U-shaped grooves formed therein. The plates form congruent halves wherein matching grooves complete independent heat pipes. The bight section of each heat pipe serves as an evaporator section while the parallel arms of each heat pipe form condenser sections.
U.S. Pat. No. 3,792,318 discloses an improved cooling apparatus for flat semiconductors in which the semiconductor is held between two base members. Each one of the two base members has one or more heat pipes inserted into holes formed therein. Heat is conducted by the vaporized working fluid in the heat pipe from the end inserted into the base member to other end which contains cooling fins which condense the vapor. Once in a liquid form, it then returns by capillary action through a wick. The cooling fins may be located remote from the semiconductor to take advantage of more favorable cooling conditions.
U.S. Pat. No. 3,786,861 discloses a heat pipe comprising a fluid-tight container for transferring heat from a source adjacent to an evaporation region to a sink adjacent to a condenser region. The heat pipe also includes a passage for transferring vapor from the evaporator region to the condenser region, and a wick having high heat conductivity for transferring condensate from the condenser region back to the evaporator region by capillary pumping. The wick also conducts heat from the container in the evaporator region to the evaporation sites, and from the condensation sites to the container in the condenser region. The wick comprises a bundle-like arrangement of substantially direct, parallel, substantially uniform capillary channels.
Until recently, portable computers have typically used a single heat pipe. The use of two or more heat pipes increases the cooling capacity. However, the disadvantages presented above limit the overall effectiveness of a multiple heat pipe cooling system. The power consumption of computer-related heat generating components such as microprocessors continues to increase, and the size of portable computers continues to decrease. As a result, a more robust cooling apparatus for portable computers is needed to ensure that a suitable operating temperature for heat generating components such as the microprocessor is maintained.
Accordingly, there is a need for a cooling apparatus that overcomes the shortcomings of previous cooling systems and techniques.